The Eastern Orthodox Church is also known as the Orthodox Church.

Foundations were laid in the pre-Chalcedonian period (up to 451) with the writings of Athanasius, Chrysostom, Cyril of Alexandria, and the Cappadocian Fathers (Basil the Great, Gregory the Theologian, Gregory of Nyssa).  The theology of these teachers found expression in the ecumenical councils of Nicaea (325), Constantinople (381) and Ephesus (431).

The early Byzantine period (451–843) included what was, for the Orthodox, the last ecumenical council (Nicaea, 787).  Leading theologians included Leontius of Byzantium, Leontius of Jerusalem, Maximus the Confessor and John of Damascus.  Distinctive features of Orthodox spirituality – including the veneration of icons and the great liturgies – developed during this period.

The late Byzantine period extended to 1452.  A missionary advance, spearheaded by St. Cyril and St. Methodius, led to the converstion of Bulgaria, Serbia and Russia.  It was marked by bitter disputes with the Western church, particularly of the Filioque clause (which had been added to the Nicene Creed in the 6th century in Spain, and adopted officially at Rome around 1014).  This clause not only prompted debate about the procession of the Holy Spirit, but also concerns about papal authority.  The ‘Great Schism’ between the Western and Eastern churches is usually dated to 1054, but tensions and disagreements had been building up for a long period prior to that date.  Unsuccessful attempts at reunion were made by the Councils of Lyons (1274) and Florence (1438-9).  Influential teachers during this period included Symeon the New Theologian (949–1022) and Gregory Palamas (c. 1296–1359).

From the time of the fall of Constantinople (1453) the Church of Russia has been the most prominent member of the Orthodox communion.  During the period of Turkish domination (1453-1821), Eastern churches sent many students to be educated in the West.  This resulted in Eastern theology adopting many of the methodologies and interests of the West.

The modern period has been marked by a recovery of monasticism and by bitter persecution at the hands of Islam and Communism.  During this period, Orthodox theology came under the influence of liberal Protestantism, but a conservative tendency continues to be strong.  Some of the teaching and practice of this period has been deeply mystical.  Since the collapse of Communist power in 1988, the Orthodox churches in Russia and the rest of Eastern Europe have seen something of a revival.

Gerald Bray, art. ‘Eastern Orthodox Theology’, in New Dictionary of Theology: Historical and Systematic.

Art. ‘Orthodox Church’ in Dictionary of the Christian Church, ed. F.L. Cross & E.A. Livingstone.